The vasa vasorum are a network of tiny arteries and veins on the outer wall of major blood vessels which penetrate into the wall to supply respiration and nutrition to the vascular wall. In addition, these vessels penetrate through the arterial wall and into neovessels in the atherosclerotic plaques to provide nutrients and oxygen to the abnormal cells forming the plaque. The blood in the intraplaque neovessels is squeezed out in systole and inflates the neovessels in diastole. We are developing an ultrasound examination method that can be performed through the skin of the neck to measure the strain (deformation) of these plaques. By determining the arterial pressure when the neovessels inflate, the pressure in the vasa vasorum can be determined; the inflation volume is equal to the neovascular volume. Atherosclerotic carotid artery plaques which have a large neovascular volume are vulnerable to rupture, causing a stroke. The ultrasonic measurement developed in this project will differentiate such plaques from those that are stable. In this study we will measure the plaque strain in 300 patients to provide a distribution of normal and abnormal strain values in the people who have stenotic atherosclerotic carotid artery plaques. [unreadable] [unreadable] [unreadable]